Cumulative exposure to reactive oxygen species has been proposed as a root cause of the degenerative diseases of aging. The hypothesis that oxidation of low density lipoproteins (LDL) is central to the etiology of atherosclerotic cardiovascular disease has led to an explosion of interest in LDL oxidation. However, even though high density lipoproteins (HDL) play a critical role in protecting against atherosclerosis and are more susceptible to oxidation than LDL, much less attention has been directed towards the effects of oxidation on the biological properties of HDL. The PI's pilot data suggest that dietary fatty acids, antioxidant vitamins and tobacco use have a major impact on HDL plasma concentration and oxidation susceptibility. The PI will now further examine the effects of dietary fatty acids, antioxidant vitamins and tobacco use on the plasma concentration of HDL and LDL. In parallel studies he will investigate the effects of these factors on the molecular mechanisms of HDL oxidation and the manner which nutrient antioxidants modulate these reactions. The specific aims are to: 1) study the effects of dietary fatty acids, vitamins E and C, and tobacco use on HDL levels in male and female subjects; 2) study the pro- and antioxidant effects of these factors on the oxidation reactions of HDL and LDL using lipoproteins isolated from the dietary modification studies; 3) study the mechanisms of HDL oxidation and antioxidant action using recombinant HDL particles with well-defined lipid, apolipoprotein and antioxidant composition. The long-term goal of this proposal is to elucidate the specific biologic effects of dietary pro- and antioxidants on HDL oxidation. This knowledge may be important in understanding the factors that regulate HDL levels in circulation and could suggest new dietary approaches to the prevention of atherosclerotic cardiovascular disease.